Don't get sidetracked into any "I pay insurance and road tax, I don't drive a chav Saxo" rants, don't bother that the Policeman said "it looked loud", conentrate on the fact that your car didn't break any rules by being at X db at Y rpm.

Is that right though? From the way this has been explained, there is no rule of X db at Y rpm for the rpm used to test. The measure they have gives the measure it does, but the test should have been (as I understand it) Y-1500, for which there is currently no reading available. At Y-1500 the vehicle may or may not have been in contravention, but does that actually matter in this instance?

My view is that if they have no reading for Y-1500 RPM (the appropriate testing speed), then they have no evidence of any rule being broken, other than "it looks a bit loud"

Exactly. So why did you say concentrate on 'the fact that your car didn't break any rules by being at X db at Y rpm' rather than they have no evidence of a rule being broken. The case would be without merit surely.

By the ridiculous standards of this test OP was subjected to, no standard Type R would pass the test anyway since they are 93db by most measures, so I'm not too worried about my aftermarket kit being non-compliant with these draconian and moronic rules. By a quick look at your garage, not a single one of your cars would pass the test either!

Yes, I have their (Norfolk Police) paperwork which quotes noise test done in accordance with ISO5130 and have a copy of the latest ISO5130 which differs from the police form. As I have said earlier, they checked my car at 5250 RPM, ISO5130 states the test to be done ar 3750RPM. If my maths is correct, that is 1500RPM lower than the Police checked it at THAT is what I am arguing about

That's what you should concentrate on. Anything else is irrelevant. The test was defective as it was not carried out in accordance with ISO5130. I am surprised they made such a simple yet fundamental error because the information is readily available on the internet.

Their actions smack of a zeal to implement a crack down coupled with reliance on the premise that nobody cba to mount a challenge over a £30 FPN which doesn't carry points.

I have a Noble and the exhaust is around 99db (tested at a track). Yes, it is loud but i have never had a problem with the police. If i did get a difficult copper, what could they do? don't they have to test your car based on how loud a standard car would be?

Since when was there an official dB limit? I have always believed that as long as your car complied with the regs current at the time of its manufacture, you were fine. (Apart from one or two safety areas).

My GT3, completely standard, easily makes 100dB on a trackday test at 75% of maximum revs and gets even noisier after that but it still complies with the manufacturers settings. Illegal? It idles at well over the maximum number mentioned by the OP too, so surely I should be nicked and fined every time I drive it.